#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main()
{
	int arr[10] = {1,2,3,4,5,1,2,3,4};
	int sz = sizeof(arr) / sizeof(arr[0]);
	int ret = 0;
	for (int i = 0; i < sz; i++)
	{
		ret ^= arr[i];
	}
	printf("%d", ret);
	return 0;
}